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Model Comparison

Claude Sonnet 5.5 vs Solar Pro 4Which Is Better in 2026?

Anthropic: Claude Sonnet 5.5 logoAnthropic•
Upstage

Claude Sonnet 5.5 vs Solar Pro 4: which should you choose in 2026?

Claude Sonnet 5.5 (by Anthropic) and Solar Pro 4 (by Upstage) are compared below. Here is how they stack up on benchmarks, price, and capabilities, and which one to pick in 2026.

There are not enough shared, protocol-compatible benchmark results to declare a performance leader.

Solar Pro 4 is about 25.4× cheaper on a blended 3:1 input/output basis ($0.1575 vs $4.00 per 1M tokens).

Claude Sonnet 5.5 has the larger context window (1,000,000 tokens vs 524,288 tokens).

Choose Claude Sonnet 5.5 if…

  • • you work with longer documents, transcripts, or codebases
  • • you need image inputs

Choose Solar Pro 4 if…

  • • lower blended API cost matters for your workload

The benchmark count includes only results measured with a matching benchmark version and protocol. Arena scores are shown separately. Missing, preliminary, and incompatible data is not treated as a controlled win. Published point-score comparisons are labeled separately when protocol details are incomplete. For text-output models, the verdict also compares token pricing and context windows.

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Performance benchmarks

Every value links to its source. A dash means that no reviewed result is available for that exact model and protocol.

Claude Sonnet 5.5 and Solar Pro 4 benchmark results
BenchmarkClaude Sonnet 5.5Solar Pro 4
AutomationBench-AA

A 657-task benchmark of multi-step work across simulated SaaS applications in six business domains. The Artificial Analysis protocol reports a guardrail-aware score and is distinct from both the public Zapier split and the unrelated dynamic AutoBench framework.

Guardrail-aware score

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BrowseComp

A benchmark of difficult, verifiable information-seeking questions designed to measure an agent's ability to locate hard-to-find facts through web browsing.

Accuracy

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OSWorld-Verified

A verified computer-use benchmark in which multimodal agents operate desktop applications and are graded from the resulting environment state.

Mean task reward

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SWE-Bench Verified

A human-validated subset of real GitHub issues used to measure whether a coding agent can produce repository patches that resolve the associated tests.

Resolved

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Terminal-Bench 2.1

Version 2.1 of the benchmark for completing realistic tasks in terminal environments. Harness, resource limits, and attempt count are part of the protocol.

Mean task success

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AutoBench

A dynamic LLM evaluation framework in which models generate questions, answer them, and participate in reciprocal peer assessment. AutoBench is distinct from Zapier's AutomationBench.

Weighted peer-assessment score

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GPQA Diamond

The highest-quality subset of Graduate-Level Google-Proof Q&A, designed to test expert-level scientific reasoning in biology, physics, and chemistry.

Accuracy

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Humanity's Last Exam

A 2,500-question expert-level benchmark spanning dozens of academic fields. Tool-assisted and no-tools results are separate protocols and must not be merged.

Accuracy

——
Arena preference scores
Arena (Text)

Human preference score

—
1386 ±6
Arena (Code/WebDev)

Human preference score for code and web development

—
1370 ±10

Benchmark sources

Reviewed evidence last updated 2026-08-09. Arena data last refreshed Oct 5, 2026.

Pricing, capabilities, and model facts

Claude Sonnet 5.5 and Solar Pro 4 model facts
FeatureClaude Sonnet 5.5Solar Pro 4
Context & model facts
DeveloperAnthropicUpstage
API providerAnthropicUpstage
Input context1,000,000 tokens524,288 tokens
Maximum output128,000 tokens131,072 tokens
Released——
Added to WritingmateSep 28, 2026Aug 10, 2026
LicenseNot availableNot available
Knowledge cutoff——
Capabilities
InputsText, Image, FileText
OutputsTextText
Provider endpoint accepts tool parametersYesYes
ReasoningYesYes
VisionYesNo
Image GenerationNoNo
Video GenerationNoNo
API pricing
Input (per 1M tokens)$2.00$0.09
Output (per 1M tokens)$10.00$0.36
Blended 3:1 input/output$4.00$0.1575
API performance
p95 latencyNot measuredNot measured
Output throughputNot measuredNot measured
Writingmate shows API performance only when both models have enough observations from the same measurement window, prompt profile, and provider. Third-party latency values are not copied into this table.

Data sources

  • Writingmate model catalog (pricing, limits, and availability)

Catalog data last updated Sep 28, 2026.

Why Pay for Multiple Subscriptions?

Comparing Claude Sonnet 5.5 from Anthropic with Solar Pro 4 from Upstage? Instead of managing separate API keys and subscriptions, get both with Writingmate.

Subscription-plan access for Claude Sonnet 5.5 and Solar Pro 4
PlanPriceClaude Sonnet 5.5Solar Pro 4AI ImagesAI Video
Writingmate Pro
Most popular
$20/moIncludedIncludedNano Banana Pro, FLUX.2, DALL-E & moreVEO 3.1, Kling 3.0
Writingmate Ultimate
Power users
$60/moIncludedIncludedNano Banana Pro, FLUX.2, DALL-E & moreVEO 3.1, Kling 3.0
View Plans & Pricing

Claude Sonnet 5.5 vs Solar Pro 4 FAQ

Which is better, Claude Sonnet 5.5 or Solar Pro 4?

There are not enough shared, protocol-compatible benchmark results to declare a performance leader. Solar Pro 4 is about 25.4× cheaper on a blended 3:1 input/output basis ($0.1575 vs $4.00 per 1M tokens). Claude Sonnet 5.5 has the larger context window (1,000,000 tokens vs 524,288 tokens).

Which model is cheaper to use through an API?

Solar Pro 4 is about 25.4× cheaper on a blended 3:1 input/output basis ($0.1575 vs $4.00 per 1M tokens).

Which model supports more context?

Claude Sonnet 5.5 has the larger context window (1,000,000 tokens vs 524,288 tokens).

Can I switch between Claude Sonnet 5.5 and Solar Pro 4?

Yes. Use the model selector on this page to open any current Writingmate model comparison. You can also run the same prompt with both models in Writingmate.